645865851 has 16 divisors (see below), whose sum is σ = 870420096. Its totient is φ = 425959296.

The previous prime is 645865789. The next prime is 645865859. The reversal of 645865851 is 158568546.

It is not a de Polignac number, because 645865851 - 2²⁶ = 578756987 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 645865851.

It is not an unprimeable number, because it can be changed into a prime (645865859) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 216496 + ... + 219458.

It is an arithmetic number, because the mean of its divisors is an integer number (54401256).

Almost surely, 2^645865851 is an apocalyptic number.

645865851 is a deficient number, since it is larger than the sum of its proper divisors (224554245).

645865851 is a wasteful number, since it uses less digits than its factorization.

645865851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3722.

The product of its digits is 1152000, while the sum is 48.

The square root of 645865851 is about 25413.8909063528. The cubic root of 645865851 is about 864.3987049262.

The spelling of 645865851 in words is "six hundred forty-five million, eight hundred sixty-five thousand, eight hundred fifty-one".